1. Field of the Invention
This invention relates to a keyswitch assembly suitable for being disposed on a keyboard. In particular, this invention relates to a keyswitch assembly capable of preventing wobbling of the key during its operation.
2. Description of Prior Art
These days, computers have become indispensable implements for daily life. Due to their high efficiency in data processing and data storage, computers are widely adopted in industry, commerce and the home. Likewise, computers are accessible to families and schools and bring convenience to people.
As to the input device of a computer, a keyboard is by far the most prevalent. The established mode of inputting data into computers with the aid of a keyboard is a succession from the manipulation of typewriters. In spite of the appearance of other tools and methods, the keyboard remains the dominant input device for computers.
FIG. 1 is a perspective exploded view showing the structure of a conventional keyswitch assembly. FIG. 2 is a perspective view, observed from the bottom thereof, showing the structure of the cap of the keyswitch assembly shown in FIG. 1. FIG. 3 is a side view showing a fabricated keyswitch assembly, wherein the cap of the keyswitch assembly is at its first (elevated) position. FIG. 4 is a side view showing the fabricated keyswitch assembly of FIG. 3, wherein the cap of the keyswitch assembly is at its second (pressed down) position.
As shown in FIGS. 1 to 4, the conventional keyswitch assembly comprises a substrate 10, a cap 12, a first connecting member 14, a second connecting member 16 and an elastic member 18. A film circuit board 11 is disposed onto the substrate 10, and two pivot supports 102 having through holes therein and an engaging hook 104 are formed on the substrate 10. The two pivot supports 102 are used for pivotally supporting the first connecting member 14 at its protrusions 142; the engaging hook 104 is used for engaging the second connecting member 16 at its rod-shaped member 164.
In fabricated state, the cap 12 is restrained to move only between the first (elevated) position (see FIG. 3) and the second (pressed down) position (see FIG. 4). As shown in FIG. 2, two through holes 122 for engaging with the rod-shaped member 162 of the second connecting member 16 and two hooks 124 for receiving the protrusions 144 of the first connecting member 14 are respectively formed on the bottom of the cap 12.
The first connecting member 14 is substantially in a "U" shape and two pairs of protrusions 142, 144 are respectively formed at its two sidewalls. As shown in FIG. 3, the protrusions 142 are pivotally disposed within the holes of the pivot supports 102, while the protrusions 144 are received within the hooks 124 of the cap 12. Furthermore, one pair of pivoting holes 146 are formed in the sidewalls of the first connecting member 14 (see FIG. 1), for accommodating the protrusions 166 of the second connecting member 16.
The second connecting member 16 is shaped like a rectangular frame; a first rod 162 and a second rod 164 are respectively formed at its two opposite ends. When assembled, the first rod 162 is accommodated within the two through holes 122 of the cap 12 and the second rod 164 is engaged with the engaging hook 104 (see FIG. 3). Furthermore, the protrusions 166 are fitted within the pivoting holes 146 of the first connecting member 14. The elastic member 18 made of rubber is disposed between the substrate 10 and the cap 12 in such a way that it always urges the cap 12 upward to keep the cap 12 at its first (elevated) position (see FIG. 3). At the time the cap 12 is pressed down (see FIG. 4), the elastic member 18 is guided to touch the film circuit board 11. When the elastic member 18 touches the film circuit board 11, the film circuit board 11 is switched into conducting state.
In the above conventional keyswitch assembly, to reduce the wavering of the cap 12 during its upward or downward movement, the clearance between the hooks 124 of the cap 12 and the protrusions 144 of the first connecting member 14 is kept small. However, this will induce interference between the hooks 124 and the first connecting member 14 during operation. In the worst case, the movement of the cap 12 gets jammed. In light of the above, the clearance between the hooks 124 of the cap 12 and the protrusions 144 of the first connecting member 14 is allowed to have a large value, which will intensify the wavering of the cap 12 during its operation. The same situation occurs to the engaging hook 104 and the second rod 164 of the second connecting member 16.